The Recombination Activating Genes (RAG) 1/2 are important for the development and function of T ... more The Recombination Activating Genes (RAG) 1/2 are important for the development and function of T and B cells. Loss of RAG1/2 function results in severe combined immunodeficiency (SCID), which could lead to early death. We studied the prevalence of RAG1/2 mutations in ten SCID patients in Egypt. We identified two novel homozygous nonsense mutations in RAG1, a novel homozygous deletion, and a previously reported homozygous missense mutation from four patients, as well as two homozygous mutations in RAG2 from the same patient. Prenatal diagnosis performed in the mother of a patient with RAG1 deficiency determined that the fetus was heterozygous for the same mutation. This represents the first report on RAG1/2 mutations in SCID patients in Egypt. The early diagnosis dramatically affects the outcome of the disease by allowing bone marrow transplantation at an early age, and providing prenatal diagnosis and genetic counseling for families with a history of SCID.
To date, several germline mutations have been identified in the LRBA gene in patients suffering f... more To date, several germline mutations have been identified in the LRBA gene in patients suffering from a variety of clinical symptoms. These mutations abolish the expression of the LRBA protein, leading to autoimmunity, chronic diarrhea, B-cell deficiency, hypogammaglobulinemia, functional T-cell defects and aberrant autophagy. We review the clinical and laboratory features of patients with LRBA mutations and present five novel mutations in eight patients suffering from a multitude of clinical features.
Patients with a combined immunodeficiency characterized by normal numbers but impaired function o... more Patients with a combined immunodeficiency characterized by normal numbers but impaired function of T and B cells had a homozygous p.Tyr20His substitution in transferrin receptor 1 (TfR1), encoded by TFRC. The substitution disrupts the TfR1 internalization motif, resulting in defective receptor endocytosis and markedly increased TfR1 expression on the cell surface. Iron citrate rescued the lymphocyte defects, and expression of wild-type but not mutant TfR1 rescued impaired transferrin uptake in patient-derived fibroblasts. Tfrc(Y20H/Y20H) mice recapitulated the immunological defects of patients. Despite the critical role of TfR1 in erythrocyte development and function, patients had only mild anemia and only slightly increased TfR1 expression in erythroid precursors. We show that STEAP3, a metalloreductase expressed in erythroblasts, associates with TfR1 and partially rescues transferrin uptake in patient-derived fibroblasts, suggesting that STEAP3 may provide an accessory TfR1 endocy...
The Journal of allergy and clinical immunology, Jan 15, 2015
Coronin-1A (CORO1A) is a regulator of actin dynamics important for T-cell homeostasis. CORO1A def... more Coronin-1A (CORO1A) is a regulator of actin dynamics important for T-cell homeostasis. CORO1A deficiency causes T(-)B(+) natural killer-positive severe combined immunodeficiency or T-cell lymphopenia with severe viral infections. However, because all known human mutations in CORO1A abrogate protein expression, the role of the protein's functional domains in host immunity is unknown. We sought to identify the cause of the primary immunodeficiency in 2 young adult siblings with a history of disseminated varicella, cutaneous warts, and CD4(+) T-cell lymphopenia. We performed immunologic, genetic, and biochemical studies in the patients, family members, and healthy control subjects. Both patients had CD4(+) T-cell lymphopenia and decreased lymphocyte proliferation to mitogens. IgG, IgM, IgA, and specific antibody responses were normal. Whole-genome sequencing identified a homozygous frameshift mutation in CORO1A disrupting the last 2 C-terminal domains by replacing 61 amino acids wi...
The alpha1,2-mannosidase Mns1p involved in the N-glycosidic pathway in Saccharomyces cerevisiae i... more The alpha1,2-mannosidase Mns1p involved in the N-glycosidic pathway in Saccharomyces cerevisiae is a type II membrane protein of the endoplasmic reticulum. The localization of Mns1p depends on retrieval from the Golgi through a mechanism that involves Rer1p. A chimera consisting of the transmembrane domain of Mns1p fused to the catalytic domain of the Golgi alpha1,2-mannosyltransferase Kre2p was localized in the endoplasmic reticulum of Deltapep4 cells and in the vacuoles of rer1/Deltapep4 by indirect immunofluorescence. The split-ubiquitin system was used to determine if there is an interaction between Mns1p and Rer1p in vivo. Co-expression of NubG-Mns1p and Rer1p-Cub-protein A-lexA-VP16 in L40 yeast cells resulted in cleavage of the reporter molecule, protein A-lexA-VP16, detected by western blot analysis and by expression of beta-galactosidase activity. Sec12p, another endoplasmic reticulum protein that depends on Rer1p for its localization, also interacted with Rer1p using the s...
In this thesis, the mechanism of endoplasmic reticulum localization of Saccharomyces cerevisiae a... more In this thesis, the mechanism of endoplasmic reticulum localization of Saccharomyces cerevisiae alpha1,2-mannosidase is studied. alpha1,2-mannosidase is a type II membrane glycoprotein localized in the endoplasmic reticulum, yet it does not have any of the known endoplasmic reticulum localization signals. Immunofluorescence studies show that the endoplasmic reticulum localization of alpha1,2-mannosidase depends on the Golgi protein Rer1p, since in rer1-deleted cells, alpha1,2-mannosidase migrates to the vacuoles. Furthermore, alpha1,2-mannosidase acquires Golgi-specific carbohydrate modification. These results show that the steady state endoplasmic reticulum localization of alpha1,2-mannosidase involves recycling from the Golgi apparatus. The transmembrane domain of alpha1,2-mannosidase is important for endoplasmic reticulum localization since fusing it to the Golgi protein Kre2p results in the endoplasmic reticulum localization of the chimera in an Rer1p-dependent manner. Mutation ...
Background Combined immunodeficiencies are marked by inborn errors of T-cell immunity in which th... more Background Combined immunodeficiencies are marked by inborn errors of T-cell immunity in which the T cells that are present are quantitatively or functionally deficient. Impaired humoral immunity is also common. Patients have severe infections, autoimmunity, or both. The specific molecular, cellular, and clinical features of many types of combined immunodeficiencies remain unknown. Methods We performed genetic and cellular immunologic studies involving five unrelated children with early-onset invasive bacterial and viral infections, lymphopenia, and defective T-cell, B-cell, and natural killer (NK)-cell responses. Two patients died early in childhood; after allogeneic hematopoietic stem-cell transplantation, the other three had normalization of T-cell function and clinical improvement. Results We identified biallelic mutations in the dedicator of cytokinesis 2 gene (DOCK2) in these five patients. RAC1 activation was impaired in the T cells. Chemokine-induced migration and actin polymerization were defective in the T cells, B cells, and NK cells. NK-cell degranulation was also affected. Interferon-α and interferon-λ production by peripheral-blood mononuclear cells was diminished after viral infection. Moreover, in DOCK2-deficient fibroblasts, viral replication was increased and virus-induced cell death was enhanced; these conditions were normalized by treatment with interferon alfa-2b or after expression of wild-type DOCK2. Conclusions Autosomal recessive DOCK2 deficiency is a new mendelian disorder with pleiotropic defects of hematopoietic and nonhematopoietic immunity. Children with clinical features of combined immunodeficiencies, especially with early-onset, invasive infections, may have this condition. (Supported by the National Institutes of Health and others.).
Journal of immunology (Baltimore, Md. : 1950), Jan 13, 2015
The Rho GTPase Cdc42 coordinates regulation of the actin and the microtubule cytoskeleton by bind... more The Rho GTPase Cdc42 coordinates regulation of the actin and the microtubule cytoskeleton by binding and activating the Wiskott-Aldrich syndrome protein. We sought to define the role of intrinsic expression of Cdc42 by mature B cells in their activation and function. Mice with inducible deletion of Cdc42 in mature B cells formed smaller germinal centers and had a reduced Ab response, mostly of low affinity to T cell-dependent Ag, compared with wild-type (WT) controls. Spreading formation of long protrusions that contain F-actin, microtubules, and Cdc42-interacting protein 4, and assumption of a dendritic cell morphology in response to anti-CD40 plus IL-4 were impaired in Cdc42-deficient B cells compared with WT B cells. Cdc42-deficient B cells had an intact migratory response to chemokine in vitro, but their homing to the B cell follicles in the spleen in vivo was significantly impaired. Cdc42-deficient B cells induced a skewed cytokine response in CD4(+) T cells, compared with WT B...
The actin cytoskeleton is essential for cell adhesion and migration, functions important for tumo... more The actin cytoskeleton is essential for cell adhesion and migration, functions important for tumor invasion. In addition to binding N-WASP/WASP, WIP binds and stabilizes F-actin. WIP ØŠ/ØŠ fibroblasts were used to test the role of WIP in F-actin function. WIP ØŠ/ØŠ cells had defective focal adhesion (FA), stress fiber assembly, and adherence to substrates, functions that were restored by transduction of wild-type WIP. Protein and mRNA levels of several FA constituents regulated by the myocardin-related transcription factor (MRTF)-serum response factor (SRF) transcription factor complex were reduced in WIP ØŠ/ØŠ fibroblasts. The level of G-actin, which sequesters MRTF in the cytoplasm, was increased, and nuclear localization of MRTF-A and SRF was reduced, in WIP ØŠ/ØŠ fibroblasts. Transfection of an MRTF-A mutant that constitutively translocates to the nucleus or transfection of constitutively active SRF restored FA and stress fiber assembly. Fibroblasts from knock-in mice expressing a WIP mutant that fails to bind actin phenocopied WIP ØŠ/ØŠ fibroblasts. Thus, WIP is a novel regulator of FA assembly and cell adhesion.
Combined immunodeficiency (CID) is characterized by severe recurrent infections with normal numbe... more Combined immunodeficiency (CID) is characterized by severe recurrent infections with normal numbers of T and B lymphocytes but with deficient cellular and humoral immunity. Most cases are sporadic, but autosomal recessive inheritance has been described. In most cases, the cause of CID remains unknown. We wanted to identify the genetic cause of CID in 2 siblings, the products of a first-cousin marriage, who experienced recurrent bacterial and candidal infections with bronchiectasis, growth delay, and early death. We performed immunologic, genetic, and biochemical studies in the 2 siblings, their family members, and healthy controls. Reconstitution studies were performed with T cells from mucosa-associated lymphoid tissue lymphoma-translocation gene 1-deficient (Malt1(-/-)) mice. The numbers of circulating T and B lymphocytes were normal, but T-cell proliferation to antigens and antibody responses to vaccination were severely impaired in both patients. Whole genome sequencing of 1 patient and her parents, followed by DNA sequencing of family members and healthy controls, showed the presence in both patients of a homozygous missense mutation in MALT1 that resulted in loss of protein expression. Analysis of T cells that were available on one of the patients showed severely impaired IκBα degradation and IL-2 production after activation, 2 events that depend on MALT1. In contrast to wild-type human MALT1, the patients' MALT1 mutant failed to correct defective nuclear factor-κB activation and IL-2 production in MALT1-deficient mouse T cells. An autosomal recessive form of CID is associated with homozygous mutations in MALT1. If future patients are found to be similarly affected, they should be considered as candidates for allogeneic hematopoietic cell transplantation.
Background: Clinical immunology has traditionally relied on accurate phenotyping of the patient's... more Background: Clinical immunology has traditionally relied on accurate phenotyping of the patient's immune dysfunction for the identification of a candidate gene or genes for sequencing and molecular confirmation. Although this is also true for other branches of medicine, the marked variability in immune-related phenotypes and the highly complex network of molecules that confer normal host immunity are challenges that clinical immunologists often face in their quest to establish a specific genetic diagnosis. Objective: We sought to identify the underlying genetic cause in a consanguineous family with chronic inflammatory bowel disease-like disorder and combined immunodeficiency. Methods: We performed exome sequencing followed by autozygome filtration. Results: A truncating mutation in LPS-responsive beige-like anchor (LRBA), which abolished protein expression, was identified as the most likely candidate variant in this family. Conclusion: The combined exome sequencing and autozygosity mapping approach is a powerful tool in the study of atypical immune dysfunctions. We identify LRBA as a novel immunodeficiency candidate gene the precise role of which in the immune system requires future studies. (J Allergy Clin Immunol 2012;130:481-8.)
Deficiency of dedicator of cytokinesis 8 (DOCK8) is a newly described combined primary immunodefi... more Deficiency of dedicator of cytokinesis 8 (DOCK8) is a newly described combined primary immunodeficiency disease. It was found to account for 15% of combined immune deficiency cases in the National Primary Immunodeficiency Disorders Registry in Kuwait, a country with high prevalence of consanguinity. We present the clinical, immunologic and molecular characteristics of 9 Kuwaiti patients with DOCK8 deficiency and discuss differences that distinguish DOCK8 deficiency from atopic dermatitis. Clinical immunologists in areas with high incidence of consanguinity should have a high index of suspicion of DOCK8 deficiency in children with recalcitrant eczema, recurrent noncutaneous infections and lymphopenia.
X-linked lymphoproliferative (XLP) disease is a primary immunodeficiency syndrome associated with... more X-linked lymphoproliferative (XLP) disease is a primary immunodeficiency syndrome associated with the inability to control Epstein-Barr virus (EBV), lymphoma, and hypogammaglobulinemia. XLP is caused by mutations in the SH2D1A gene, which encodes the SLAM-associated protein (SAP), or in the BIRC4 gene, which encodes the X-linked inhibitor of apoptosis protein (XIAP). Here we report a patient with recurrent respiratory tract infections and early onset agammaglobulinemia who carried a unique disease-causing intronic loss-of-function mutation in SH2D1A. The intronic mutation affected SH2D1A gene transcription but not mRNA splicing, and led to markedly reduced level of SAP protein. Despite undetectable serum immunoglobulins, the patient's B cells replicated and differentiated into antibody producing cells normally in vitro.
We report 2 children with X-linked chronic granulomatous disease (X-CGD) who underwent hematopoie... more We report 2 children with X-linked chronic granulomatous disease (X-CGD) who underwent hematopoietic stem cell transplantation (HSCT) using grafts from their siblings selected before implantation to be both unaffected and HLA-matched donors. Preimplantation genetic diagnosis (PGD) along with HLA-typing were performed on preimplantation embryos by single-cell multiplex polymerase chain reaction using informative short tandem repeat markers in the HLA locus together with the gene region containing the mutations. Two singleton pregnancies resulted from the intrauterine transfer of selected embryos; these developed to term, producing 1 healthy female and 1 X-CGD carrier female, which are HLA-identical siblings to the 2 affected children. Combined grafts of umbilical cord blood (UCB) and bone marrow (BM) stem cells were administered to the recipients after myeloablative (MA) conditioning at the ages of 4.5 years and 4 years, respectively. Both patients are well, with complete donor hematopoietic and immunologic reconstitution, at 18 and 13 months posttransplantation, respectively. This report demonstrates that HSCT with HLA-matched sibling donors created by PGD/HLA typing of in vitro fertilized embryos is a realistic therapeutic option and should be presented as such to families with children who require a non-urgent HSCT but lack an HLA-genoidentical donor.
The Recombination Activating Genes (RAG) 1/2 are important for the development and function of T ... more The Recombination Activating Genes (RAG) 1/2 are important for the development and function of T and B cells. Loss of RAG1/2 function results in severe combined immunodeficiency (SCID), which could lead to early death. We studied the prevalence of RAG1/2 mutations in ten SCID patients in Egypt. We identified two novel homozygous nonsense mutations in RAG1, a novel homozygous deletion, and a previously reported homozygous missense mutation from four patients, as well as two homozygous mutations in RAG2 from the same patient. Prenatal diagnosis performed in the mother of a patient with RAG1 deficiency determined that the fetus was heterozygous for the same mutation. This represents the first report on RAG1/2 mutations in SCID patients in Egypt. The early diagnosis dramatically affects the outcome of the disease by allowing bone marrow transplantation at an early age, and providing prenatal diagnosis and genetic counseling for families with a history of SCID.
To date, several germline mutations have been identified in the LRBA gene in patients suffering f... more To date, several germline mutations have been identified in the LRBA gene in patients suffering from a variety of clinical symptoms. These mutations abolish the expression of the LRBA protein, leading to autoimmunity, chronic diarrhea, B-cell deficiency, hypogammaglobulinemia, functional T-cell defects and aberrant autophagy. We review the clinical and laboratory features of patients with LRBA mutations and present five novel mutations in eight patients suffering from a multitude of clinical features.
Patients with a combined immunodeficiency characterized by normal numbers but impaired function o... more Patients with a combined immunodeficiency characterized by normal numbers but impaired function of T and B cells had a homozygous p.Tyr20His substitution in transferrin receptor 1 (TfR1), encoded by TFRC. The substitution disrupts the TfR1 internalization motif, resulting in defective receptor endocytosis and markedly increased TfR1 expression on the cell surface. Iron citrate rescued the lymphocyte defects, and expression of wild-type but not mutant TfR1 rescued impaired transferrin uptake in patient-derived fibroblasts. Tfrc(Y20H/Y20H) mice recapitulated the immunological defects of patients. Despite the critical role of TfR1 in erythrocyte development and function, patients had only mild anemia and only slightly increased TfR1 expression in erythroid precursors. We show that STEAP3, a metalloreductase expressed in erythroblasts, associates with TfR1 and partially rescues transferrin uptake in patient-derived fibroblasts, suggesting that STEAP3 may provide an accessory TfR1 endocy...
The Journal of allergy and clinical immunology, Jan 15, 2015
Coronin-1A (CORO1A) is a regulator of actin dynamics important for T-cell homeostasis. CORO1A def... more Coronin-1A (CORO1A) is a regulator of actin dynamics important for T-cell homeostasis. CORO1A deficiency causes T(-)B(+) natural killer-positive severe combined immunodeficiency or T-cell lymphopenia with severe viral infections. However, because all known human mutations in CORO1A abrogate protein expression, the role of the protein's functional domains in host immunity is unknown. We sought to identify the cause of the primary immunodeficiency in 2 young adult siblings with a history of disseminated varicella, cutaneous warts, and CD4(+) T-cell lymphopenia. We performed immunologic, genetic, and biochemical studies in the patients, family members, and healthy control subjects. Both patients had CD4(+) T-cell lymphopenia and decreased lymphocyte proliferation to mitogens. IgG, IgM, IgA, and specific antibody responses were normal. Whole-genome sequencing identified a homozygous frameshift mutation in CORO1A disrupting the last 2 C-terminal domains by replacing 61 amino acids wi...
The alpha1,2-mannosidase Mns1p involved in the N-glycosidic pathway in Saccharomyces cerevisiae i... more The alpha1,2-mannosidase Mns1p involved in the N-glycosidic pathway in Saccharomyces cerevisiae is a type II membrane protein of the endoplasmic reticulum. The localization of Mns1p depends on retrieval from the Golgi through a mechanism that involves Rer1p. A chimera consisting of the transmembrane domain of Mns1p fused to the catalytic domain of the Golgi alpha1,2-mannosyltransferase Kre2p was localized in the endoplasmic reticulum of Deltapep4 cells and in the vacuoles of rer1/Deltapep4 by indirect immunofluorescence. The split-ubiquitin system was used to determine if there is an interaction between Mns1p and Rer1p in vivo. Co-expression of NubG-Mns1p and Rer1p-Cub-protein A-lexA-VP16 in L40 yeast cells resulted in cleavage of the reporter molecule, protein A-lexA-VP16, detected by western blot analysis and by expression of beta-galactosidase activity. Sec12p, another endoplasmic reticulum protein that depends on Rer1p for its localization, also interacted with Rer1p using the s...
In this thesis, the mechanism of endoplasmic reticulum localization of Saccharomyces cerevisiae a... more In this thesis, the mechanism of endoplasmic reticulum localization of Saccharomyces cerevisiae alpha1,2-mannosidase is studied. alpha1,2-mannosidase is a type II membrane glycoprotein localized in the endoplasmic reticulum, yet it does not have any of the known endoplasmic reticulum localization signals. Immunofluorescence studies show that the endoplasmic reticulum localization of alpha1,2-mannosidase depends on the Golgi protein Rer1p, since in rer1-deleted cells, alpha1,2-mannosidase migrates to the vacuoles. Furthermore, alpha1,2-mannosidase acquires Golgi-specific carbohydrate modification. These results show that the steady state endoplasmic reticulum localization of alpha1,2-mannosidase involves recycling from the Golgi apparatus. The transmembrane domain of alpha1,2-mannosidase is important for endoplasmic reticulum localization since fusing it to the Golgi protein Kre2p results in the endoplasmic reticulum localization of the chimera in an Rer1p-dependent manner. Mutation ...
Background Combined immunodeficiencies are marked by inborn errors of T-cell immunity in which th... more Background Combined immunodeficiencies are marked by inborn errors of T-cell immunity in which the T cells that are present are quantitatively or functionally deficient. Impaired humoral immunity is also common. Patients have severe infections, autoimmunity, or both. The specific molecular, cellular, and clinical features of many types of combined immunodeficiencies remain unknown. Methods We performed genetic and cellular immunologic studies involving five unrelated children with early-onset invasive bacterial and viral infections, lymphopenia, and defective T-cell, B-cell, and natural killer (NK)-cell responses. Two patients died early in childhood; after allogeneic hematopoietic stem-cell transplantation, the other three had normalization of T-cell function and clinical improvement. Results We identified biallelic mutations in the dedicator of cytokinesis 2 gene (DOCK2) in these five patients. RAC1 activation was impaired in the T cells. Chemokine-induced migration and actin polymerization were defective in the T cells, B cells, and NK cells. NK-cell degranulation was also affected. Interferon-α and interferon-λ production by peripheral-blood mononuclear cells was diminished after viral infection. Moreover, in DOCK2-deficient fibroblasts, viral replication was increased and virus-induced cell death was enhanced; these conditions were normalized by treatment with interferon alfa-2b or after expression of wild-type DOCK2. Conclusions Autosomal recessive DOCK2 deficiency is a new mendelian disorder with pleiotropic defects of hematopoietic and nonhematopoietic immunity. Children with clinical features of combined immunodeficiencies, especially with early-onset, invasive infections, may have this condition. (Supported by the National Institutes of Health and others.).
Journal of immunology (Baltimore, Md. : 1950), Jan 13, 2015
The Rho GTPase Cdc42 coordinates regulation of the actin and the microtubule cytoskeleton by bind... more The Rho GTPase Cdc42 coordinates regulation of the actin and the microtubule cytoskeleton by binding and activating the Wiskott-Aldrich syndrome protein. We sought to define the role of intrinsic expression of Cdc42 by mature B cells in their activation and function. Mice with inducible deletion of Cdc42 in mature B cells formed smaller germinal centers and had a reduced Ab response, mostly of low affinity to T cell-dependent Ag, compared with wild-type (WT) controls. Spreading formation of long protrusions that contain F-actin, microtubules, and Cdc42-interacting protein 4, and assumption of a dendritic cell morphology in response to anti-CD40 plus IL-4 were impaired in Cdc42-deficient B cells compared with WT B cells. Cdc42-deficient B cells had an intact migratory response to chemokine in vitro, but their homing to the B cell follicles in the spleen in vivo was significantly impaired. Cdc42-deficient B cells induced a skewed cytokine response in CD4(+) T cells, compared with WT B...
The actin cytoskeleton is essential for cell adhesion and migration, functions important for tumo... more The actin cytoskeleton is essential for cell adhesion and migration, functions important for tumor invasion. In addition to binding N-WASP/WASP, WIP binds and stabilizes F-actin. WIP ØŠ/ØŠ fibroblasts were used to test the role of WIP in F-actin function. WIP ØŠ/ØŠ cells had defective focal adhesion (FA), stress fiber assembly, and adherence to substrates, functions that were restored by transduction of wild-type WIP. Protein and mRNA levels of several FA constituents regulated by the myocardin-related transcription factor (MRTF)-serum response factor (SRF) transcription factor complex were reduced in WIP ØŠ/ØŠ fibroblasts. The level of G-actin, which sequesters MRTF in the cytoplasm, was increased, and nuclear localization of MRTF-A and SRF was reduced, in WIP ØŠ/ØŠ fibroblasts. Transfection of an MRTF-A mutant that constitutively translocates to the nucleus or transfection of constitutively active SRF restored FA and stress fiber assembly. Fibroblasts from knock-in mice expressing a WIP mutant that fails to bind actin phenocopied WIP ØŠ/ØŠ fibroblasts. Thus, WIP is a novel regulator of FA assembly and cell adhesion.
Combined immunodeficiency (CID) is characterized by severe recurrent infections with normal numbe... more Combined immunodeficiency (CID) is characterized by severe recurrent infections with normal numbers of T and B lymphocytes but with deficient cellular and humoral immunity. Most cases are sporadic, but autosomal recessive inheritance has been described. In most cases, the cause of CID remains unknown. We wanted to identify the genetic cause of CID in 2 siblings, the products of a first-cousin marriage, who experienced recurrent bacterial and candidal infections with bronchiectasis, growth delay, and early death. We performed immunologic, genetic, and biochemical studies in the 2 siblings, their family members, and healthy controls. Reconstitution studies were performed with T cells from mucosa-associated lymphoid tissue lymphoma-translocation gene 1-deficient (Malt1(-/-)) mice. The numbers of circulating T and B lymphocytes were normal, but T-cell proliferation to antigens and antibody responses to vaccination were severely impaired in both patients. Whole genome sequencing of 1 patient and her parents, followed by DNA sequencing of family members and healthy controls, showed the presence in both patients of a homozygous missense mutation in MALT1 that resulted in loss of protein expression. Analysis of T cells that were available on one of the patients showed severely impaired IκBα degradation and IL-2 production after activation, 2 events that depend on MALT1. In contrast to wild-type human MALT1, the patients' MALT1 mutant failed to correct defective nuclear factor-κB activation and IL-2 production in MALT1-deficient mouse T cells. An autosomal recessive form of CID is associated with homozygous mutations in MALT1. If future patients are found to be similarly affected, they should be considered as candidates for allogeneic hematopoietic cell transplantation.
Background: Clinical immunology has traditionally relied on accurate phenotyping of the patient's... more Background: Clinical immunology has traditionally relied on accurate phenotyping of the patient's immune dysfunction for the identification of a candidate gene or genes for sequencing and molecular confirmation. Although this is also true for other branches of medicine, the marked variability in immune-related phenotypes and the highly complex network of molecules that confer normal host immunity are challenges that clinical immunologists often face in their quest to establish a specific genetic diagnosis. Objective: We sought to identify the underlying genetic cause in a consanguineous family with chronic inflammatory bowel disease-like disorder and combined immunodeficiency. Methods: We performed exome sequencing followed by autozygome filtration. Results: A truncating mutation in LPS-responsive beige-like anchor (LRBA), which abolished protein expression, was identified as the most likely candidate variant in this family. Conclusion: The combined exome sequencing and autozygosity mapping approach is a powerful tool in the study of atypical immune dysfunctions. We identify LRBA as a novel immunodeficiency candidate gene the precise role of which in the immune system requires future studies. (J Allergy Clin Immunol 2012;130:481-8.)
Deficiency of dedicator of cytokinesis 8 (DOCK8) is a newly described combined primary immunodefi... more Deficiency of dedicator of cytokinesis 8 (DOCK8) is a newly described combined primary immunodeficiency disease. It was found to account for 15% of combined immune deficiency cases in the National Primary Immunodeficiency Disorders Registry in Kuwait, a country with high prevalence of consanguinity. We present the clinical, immunologic and molecular characteristics of 9 Kuwaiti patients with DOCK8 deficiency and discuss differences that distinguish DOCK8 deficiency from atopic dermatitis. Clinical immunologists in areas with high incidence of consanguinity should have a high index of suspicion of DOCK8 deficiency in children with recalcitrant eczema, recurrent noncutaneous infections and lymphopenia.
X-linked lymphoproliferative (XLP) disease is a primary immunodeficiency syndrome associated with... more X-linked lymphoproliferative (XLP) disease is a primary immunodeficiency syndrome associated with the inability to control Epstein-Barr virus (EBV), lymphoma, and hypogammaglobulinemia. XLP is caused by mutations in the SH2D1A gene, which encodes the SLAM-associated protein (SAP), or in the BIRC4 gene, which encodes the X-linked inhibitor of apoptosis protein (XIAP). Here we report a patient with recurrent respiratory tract infections and early onset agammaglobulinemia who carried a unique disease-causing intronic loss-of-function mutation in SH2D1A. The intronic mutation affected SH2D1A gene transcription but not mRNA splicing, and led to markedly reduced level of SAP protein. Despite undetectable serum immunoglobulins, the patient's B cells replicated and differentiated into antibody producing cells normally in vitro.
We report 2 children with X-linked chronic granulomatous disease (X-CGD) who underwent hematopoie... more We report 2 children with X-linked chronic granulomatous disease (X-CGD) who underwent hematopoietic stem cell transplantation (HSCT) using grafts from their siblings selected before implantation to be both unaffected and HLA-matched donors. Preimplantation genetic diagnosis (PGD) along with HLA-typing were performed on preimplantation embryos by single-cell multiplex polymerase chain reaction using informative short tandem repeat markers in the HLA locus together with the gene region containing the mutations. Two singleton pregnancies resulted from the intrauterine transfer of selected embryos; these developed to term, producing 1 healthy female and 1 X-CGD carrier female, which are HLA-identical siblings to the 2 affected children. Combined grafts of umbilical cord blood (UCB) and bone marrow (BM) stem cells were administered to the recipients after myeloablative (MA) conditioning at the ages of 4.5 years and 4 years, respectively. Both patients are well, with complete donor hematopoietic and immunologic reconstitution, at 18 and 13 months posttransplantation, respectively. This report demonstrates that HSCT with HLA-matched sibling donors created by PGD/HLA typing of in vitro fertilized embryos is a realistic therapeutic option and should be presented as such to families with children who require a non-urgent HSCT but lack an HLA-genoidentical donor.
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Papers by Michel Massaad